Did the valve break twice in the same spot? Same cylinder bank? Cold water on a glowing hot exhaust valve will take it out.

Of course too lean, not enough timing, can also take out exhaust valves, but normally it takes out more than 1 valve. Id take a close look at the manifolds/tails for leaks. Esp in saltwater.

[QUOTE=MILD THUNDER;3787841]Did the valve break twice in the same spot? Same cylinder bank? Cold water on a glowing hot exhaust valve will take it out.

Of course too lean, not enough timing, can also take out exhaust valves, but normally it takes out more than 1 valve. Id take a close look at the manifolds/tails for leaks. Esp the first time it was #2 this time it was #3, one thing were also thinking it was the machine shop that did the head work, this last time we orderd and took to someone else to have ferra valves put in!

If they are not inconel then it is plain old valve failure, regular valves are a 50/50 shot after 400hp period, if it was inconbel then start looking for other issues, it normally takes a lot to hurt one even with extreme lean/heat, inconel usually dont break at the stem..

This was one of my valves this summer when I had a fuel issue at went lean, this IS INCONEL, it took abuse but did not break, thats why you run them..a little more time it would have gave, I got lucky...

I will run inconel in any HP engine .....

Keep in mind that just because they are Ferea they might not be inconel. Ferea offers several grades of valves.

Yep, make sure tbey are for sure INCONEL

I dont believe Ferrea calls them "inconel". I believe they are called "super alloy" and supposedly better and lighter than a std inconel valve. I believe "inconel" was a Manley label.

Correct. "Inconel" is not a Manley patented term, but is simply a trade name for a particular stainless steel alloy that has excellent high heat strength. I think it was developed for aircraft jet turbines, particularly the vanes. I have heard good things about Ferrea's valves too - just make sure they are the super alloy and not a lesser material. FWIW, I had Ferrea exhaust valves in my previous 454, and I am pretty sure they were not the super alloys, and it lived. I have a pretty decent set of REV valves in my 489 right now. However, both of these engines were set up pretty rich, and I guess I was lucky to have never had a fuel pump start to let go, or a fuel restriction, or just a bad tank of fuel. As Full Force discovered, all it takes is one little episode that can lead to disaster and ruin an $8K+ motor. Isn't boating relaxing?

The other thing also is you want to use a quality valve seat, and stay away from fancy multi angle valve jobs that have narrow seat widths. You want to keep the seat cut on the wide side , because that is where the exhaust valve gets its cooling from.

Ad Right.... I also want to point out before I had inconel I had 2 fails where both did what the poster stated...broke ate base...one singed piston and flew out exhaust....no big deal....other one took out Liston and cracked cylinder wall.... really inconel is not cheap...but its cheaper then building engines... luckily I do my own work.....